FR2912140A1 - New N-heterocyclyl derivatives of pyridinium-substituted thiol derivative fluorescent dye compounds, useful for dyeing keratin fibers, especially for lightening dark human hair - Google Patents

Abstract

New fluorescent dye compounds (I) consist of C-(N-heterocyclyl-substituted styryl)-N-(sulfanylalkyl)-pyridinium salts or their S-substituted derivatives. Pyridinium-substituted thiol derivative fluorescent dye compounds of formula (I) and their mineral or organic acid addition salts, optical and geometric isomers, hydrates and other solvates are new. het : saturated or unsaturated N-heterocyclyl residue; R g, R' g, R h, R' hH, halo, NH 2, mono- or dialkylamino, CN, COOH, OH, CF 3, acylamino, alkoxy, 2-4C mono- or polyhydroxyalkoxy, alkylcarbonyloxy, alkoxycarbonyl, alkylcarbonylamino, acylamino, CONH 2, alkylsulfonylamino, SO 2NH 2 or 1-16C alkyl (os by 1-12C alkoxy, OH, CN, COOH, NH 2, mono- or dialkylamino or 5-7 membered N-heterocyclyl (optionally containing additional heteroatom(s)); R' i, R'' iH or alkyl; R 1 - R 4H, alkyl, alkoxy, OH, CN, COOH, mono- or dialkylamino or 5-7 membered N-heterocyclyl (optionally containing additional heteroatom(s)); T adirect bond; one or more of SO 2, O, S, N(R), -N +>(R)(R 0>)- or CO; or cationic or non-cationic heterocycloalkyl or heteroaryl; R, R 0>H, alkyl, hydroxyalkyl or aralkyl; m, n : 0-6; m + n : 1-10; M' : counter-anion; Y : H, alkali(ne earth) metal, NH 4 +>, PH 4 +>, mono-, di-, tri- or tetraalkyl-ammonium, mono-, di-, tri- or tetraalkyl-phosphonium or thiol protecting group; alkyl moieties have 1-4C unless specified otherwise; if (I) contains additional cationic moieties, at least one further counter-anion is present to preserve electro-neutrality. Independent claims are included for: (1) a dyeing composition (A) comprising (I) and optionally a reducing agent (II) in a cosmetic medium; (2) a method for dyeing keratin fibers, involving application of (A); and (3) a multi-compartment dyeing device, having a first compartment containing (I), a second compartment containing (II) and optionally a third compartment containing an oxidizing agent. [Image].

Description

DYE COMPOSITION COMPRISING A THIOL A FLUORESCENT COLORANT

  The invention relates to the dyeing of keratin materials using thiol fluorescent dyes comprising a heterocycle.

  It is known to dye keratin fibers, especially human fibers, by direct dyeing. The method conventionally used in direct dyeing consists in applying to the keratin fibers direct dyes which are colored and dyeing molecules having an affinity for the fibers, allowing them to diffuse and then rinsing the fibers. The direct dyes which are conventionally used are, for example, dyes of the nitrobenzene type, anthraquinone dyes, nitropyridines, dyes of the azo, xanthene, acridine, azine or triarylmethane type. The colorations which result from the use of direct dyes are temporary or semi-permanent dyes because the nature of the interactions which bind the direct dyes to the keratinous fiber, and their desorption from the surface and / or the core of the fiber are responsible for their low dyeing power and their poor resistance to washes or perspiration. Furthermore, the coloration of keratinous fibers from conventional direct dyes does not make it possible to significantly lighten the keratin fibers. The lightening of the color of keratinous fibers, more particularly dark to lighter shades, possibly modifying the shade thereof, constitutes an important demand. Conventionally, to obtain a lighter coloration is implemented a chemical bleaching process. This process consists of treating keratin materials such as keratin fibers, in particular the hair, with a strong oxidizing system, generally consisting of hydrogen peroxide, whether or not associated with persalts, most often in an alkaline medium. This bleaching system has the drawback of degrading keratin materials, in particular keratinous fibers, especially human fibers such as the hair, and of altering their cosmetic properties. The fibers tend to become rough, more difficult to disentangle and more fragile. Finally, the lightening or the bleaching of keratinous fibers by oxidizing agents is incompatible with the treatments for modifying the shape of said fibers, particularly in the straightening treatments. Another lightening technique consists in applying fluorescent direct dyes to dark hair. This technique described in particular in the documents FR 2830189 and WO 2004/091473 makes it possible to respect the quality of the keratinous fiber during the treatment, but the fluorescent dyes employed do not exhibit satisfactory resistance to shampooing.

  To increase the tenacity of the direct dyes, it is known to fix direct dyes by covalent bonding to the hair. For example, it is known to react dyes with reactive groups with the residues of cystine or cysteine very numerous in keratin fibers, see for example Journal of the Society of Dyers and Colourists, Guise and Stapleton, 91, 259-264 ( 1975); Journal of Cosmetic Chemistry, 42, 1-17 (1991); CA 2024509; In addition, it is known to protect the thiol function (s) contained in a molecule to be grafted to the hair before applying them to said hair W099 / 51194. However, this application does not mention the use of fluorescent dyes for coloring or lightening hair.

  The object of the present invention is to provide novel systems for dyeing keratin materials, in particular human keratinous fibers, in particular the hair, which do not have the drawbacks of existing bleaching processes. In particular, one of the aims of the present invention is to provide direct dyeing systems which make it possible to obtain lightening effects, in particular on naturally or artificially dark keratin fibers, which are stubborn in the face of successive shampoos, which do not degrade keratin fibers and which do not alter their cosmetic properties.

  This object is achieved with the present invention which relates to a process for dyeing keratin materials, in particular keratinous fibers, in particular human fibers such as the hair, more particularly the dark hair, consisting in applying to the keratin materials a dye composition. comprising, in a suitable cosmetic medium, at least one fluorescent dye thiol, chosen from the following dyes of formula (I): M 'iTa / SY CR1R2) m ~ (CR3R4) n (I) their salts of organic or mineral acid optical isomers, geometric isomers, and solvates such as hydrates; formula (I) in which:

  he represents a saturated or unsaturated heterocyclic group; particularly monocyclic comprising from 5 to 7 members and having 1 or two heteroatoms selected from nitrogen, oxygen or sulfur, particularly the heteroatom is a nitrogen atom; in particular the heterocycle is chosen from pyrazolyl, pyrrolidinyl, piperazinyl, homopiperazinyl piperidinyl, morpholinyl, and imidazolyl; - Rg, R'g, Rh and R'h, identical or different, represent a hydrogen atom, halogen, an amino group, (di) (C1-C4) alkylamino, cyano, carboxy, hydroxy, trifluoromethyl, acylamino, (C1-C4) alkoxy, (poly) hydroxyalkoxy C2-C4, (C1-C4) alkylcarbonyloxy (C1-C4) alkoxycarbonyl, (C1-C4) alkylcarbonylamino, acylamino, carbamoyl, (C1-C4) alkylsulfonylamino, a radical aminosulfonyl, or a (C1-C16) alkyl radical optionally substituted with a group chosen from (C1-C12) alkoxy, hydroxy, cyano, carboxy, amino, (di) (C1-C4) alkylamino, or both the alkyl radicals carried by the nitrogen atom of the amino group form a heterocycle comprising from 5 to 7 members and optionally comprising another heteroatom identical to or different from that of the nitrogen atom; particularly Rg, R'g, Rh and R'h represent a hydrogen atom or a (C1-C4) alkyl group; - R; and R ', which may be identical or different, represent a hydrogen atom or a (C 1 -C 4) alkyl group; particularly R; and R '; represents a hydrogen atom; -R1, R2, R3, R4, identical or different, represent a hydrogen atom or a (C1-C4) alkyl, (C1-C4) alkoxy, hydroxy, cyano, carboxy, amino, (C1-C4) alkylamino group (C1-C4) dialkylamino, said alkyl radicals being able to form, with the nitrogen atom which carries them, a 5- to 7-membered heterocycle, optionally comprising another heteroatom different or different from nitrogen; in particular R 1, R 2, R 3 and R 4 are hydrogen atoms or an amino group; especially R 1, R 2, R 3 and R 4 represent a hydrogen atom; Ta is: i) either a covalent bond a, ii) or one or more radicals or combinations thereof selected from -SO2-, -Or, uSu, uN (R) u, uN + (R) (R) u, uC ( Wherein R and R, which may be identical or different, represent a hydrogen atom, a C1-C4 alkyl radical, a C1-C4 hydroxyalkyl radical or a (C1-C4) alkyl radical; in particular, Ta represents a covalent bond a or a group chosen from ùN (R) -, ùC (O) ù, ùC (O) ùN (R) ù, ùN (R) ùC (O) ù, ùC (O) ùN (R) ùC (O) ù, where RC (O) ù, ùC (O) ùOù and ùN + (R) (R) ù, with R, R being identical or different, representing a hydrogen atom, a group C1-C4 alkyl alkyl; especially Ta represent a bond a; iii) either a heterocycloalkyl or heteroaryl radical, cationic or otherwise, preferably monocyclic, containing in particular two heteroatoms, particularly two nitrogen atoms, and in particular comprising from 5 to 7 members such as imidazolium, piperazyl, piperazinium, homopiperazyl or homopiperazinium optionally substituted with a (C1-C4) alkyl group such as methyl; m and n, identical or different, represent an integer inclusive between 0 and 6 with m + n represents an integer inclusive between 1 and 10; particularly the sum m + n is an integer inclusive between 2 and 4; preferentially m + n is an integer equal to 2; M 'representing an anionic counterion; and Y represents: i) a hydrogen atom; ii) an alkali metal; iii) an alkaline earth metal; iv) an ammonium group: N + RaRaRYR8 or a phosphonium group: P + RaRaRYR8 with Ra, Ra, R7 and R8, identical or different, representing a hydrogen atom or a (C 1 -C 4) alkyl group; or v) a thiol protecting group;

  it being understood that: - when the compound of formula (I) contains other cationic parts, it is associated with one or more anionic counter-ions making it possible to reach the electroneutrality of formula (I).

  Another subject of the invention is a dyeing composition comprising, in a suitable cosmetic medium, at least one thiol fluorescent dye of formula (I) as defined above, and optionally a reducing agent. The invention also relates to new thiol fluorescent dyes of formula (I) as defined above.

  The dyeing process according to the invention makes it possible to visibly stain dark keratin materials, in particular dark human keratin fibers, especially dark hair.

  In addition, the process of the invention makes it possible to obtain a coloration of keratinous substances, in particular human keratinous fibers, in particular the hair, without degrading said material, which is persistent with respect to shampoos, of common aggressions (sun, perspiration). ), and other hair treatments. The process of the invention also makes it possible to obtain a lightening of keratin materials such as keratinous fibers, particularly dark keratinous fibers and more particularly dark hair. For the purposes of the invention, dark keratin material is understood to mean that which has an enumerated luminescence L * in the C.I.E. L * a * b *, less than or equal to 45 and preferably less than or equal to 40, knowing moreover that L * = 0 is equivalent to black and L * = 100 to white. For the purposes of the invention, the term naturally or artificially dark hair, hair whose pitch is less than or equal to 6 (dark blonde) and preferably less than or equal to 4 (chestnut). The lightening of the hair is evaluated by the variation in pitch before and after application of the compound of formula (I). The notion of tone is based on the classification of natural nuances, a tone separating each nuance from that which follows it or immediately precedes it. This definition and the classification of natural shades is well known to hair professionals and published in the book Science of hair treatment Charles ZVIAK 1988, Ed Masson, p. 215 and 278. The pitch ranges from 1 (black) to 10 (very light blonde), a unit corresponding to a tone; the higher the number, the clearer the nuance. An artificially colored hair is a hair whose color has been modified by a coloring treatment, for example a staining with direct dyes or oxidation dyes.

  Preferably, the composition must after application to hair, for example, chestnut, bring to the results below. - We are interested in the reflectance performance of hair when irradiated with visible light in the wavelength range of 400 to 700 nanometers. The reflectance curves are then compared as a function of the wavelength, of the hair treated with the composition of the invention and of the untreated hair. - The curve corresponding to the treated hair must show a reflectance in the wavelength range from 500 to 700 nanometers higher than the curve corresponding to untreated hair. This means that, in the wavelength range of 540 to 700 nanometers, there is at least one range where the reflectance curve corresponding to the treated hair is greater than the reflectance curve corresponding to the untreated hair. The term "upper" means a difference of at least 0.05% reflectance, and preferably at least 0.1%. This does not prevent that there may exist in the wavelength range from 540 to 700 nanometers, at least one range where the reflectance curve corresponding to the treated hair is superimposable, or less than the reflectance curve corresponding to the untreated hair.

  Preferably, the wavelength where the difference is greatest between the reflectance curve of the treated hair and that of the untreated hair is in the wavelength range of 500 to 650 nanometers, and preferably in the the wavelength range from 550 to 620 nanometers.

  For the purposes of the present invention, and unless a different indication is given: the aryl or heteroaryl radicals or the aryl or heteroaryl part of a radical may be substituted by at least one substituent carried by a carbon atom, chosen from: • a C1-C16, preferably C1-C8, alkyl radical optionally substituted with one or more radicals chosen from hydroxyl, C1-C2 alkoxy and (C2-C4) poly (-hydroxyalkoxy) acylamino radicals; amino, substituted with two identical or different C1-C4 alkyl radicals, optionally bearing at least one hydroxyl group, or the two radicals being able to form, with the nitrogen atom to which they are attached, a heterocycle comprising 5- to 7-membered, preferably 5- or 6-membered, optionally substituted saturated or unsaturated group optionally comprising another heteroatom identical to or different from nitrogen; A halogen atom such as chlorine, fluorine or bromine; • a hydroxyl group; A C1-C2 alkoxy radical; A C1-C2 alkylthio radical; A C2-C4 (poly) -hydroxyalkoxy radical; An amino radical; A 5- or 6-membered heterocycloalkyl radical; A 5- or 6-membered optionally cationic heteroaryl radical, preferentially imidazolium, and optionally substituted with a (C1-C4) alkyl radical, preferably methyl; An amino radical substituted with one or two identical or different C1-C6 alkyl radicals optionally carrying at least: i) a hydroxyl group; ii) an amino group optionally substituted by one or two C1-C3 alkyl radicals; optionally substituted, said alkyl radicals being able to form, with the nitrogen atom to which they are attached, an optionally substituted 5 to 7-membered heterocyclic ring, saturated or unsaturated, optionally comprising at least one other heteroatom different from or different from nitrogen, -NR-COR 'in which the radical R is a hydrogen atom, a C1-C4 alkyl radical optionally bearing at least one hydroxyl group and the radical R' is a C1-C2 alkyl radical; (R) 2N-CO- in which the R radicals, which may be identical or different, represent a hydrogen atom or a C 1 -C 4 alkyl radical optionally bearing at least one hydroxyl group; R'SO2-NR- in which the radical R represents a hydrogen atom, a C1-C4 alkyl radical optionally bearing at least one hydroxyl group and the radical R 'represents a C1-C4 alkyl radical; phenyl radical; (R) 2N-SO 2 - in which the radicals R, which may be identical or different, represent a hydrogen atom, a C 1 -C 4 alkyl radical optionally bearing at least one hydroxyl group, a carboxylic radical in acid form or salified (preferably with an alkali metal or ammonium, substituted or unsubstituted); • a cyano group; A polyhaloalkyl group comprising from 1 to 6 carbon atoms and from 1 to 6 halogen atoms, which are identical or different, the polyhaloalkyl group is, for example, trifluoromethyl; the cyclic or heterocyclic part of a non-aromatic radical may be substituted by at least one substituent carried by a carbon atom chosen from the following groups: • hydroxy, • C 1 -C 4 alkoxy, • (poly) C 2 -C 4 hydroxyalkoxy, A C1-C2 alkylthio radical; RCO-NR'- in which the R 'radical is a hydrogen atom, a C 1 -C 4 alkyl radical optionally bearing at least one hydroxyl group and the R radical is a C 1 -C 2 alkyl substituted amino radical; by two identical or different C1-C4 alkyl groups optionally bearing at least one hydroxyl group; RCO-O- in which the radical R is a C 1 -C 4 alkyl radical, amino substituted with one or two identical or different C 1 -C 4 alkyl groups optionally bearing at least one hydroxyl group, said alkyl radicals being able to form with the nitrogen atom to which they are attached, a 5- to 7-membered optionally substituted saturated or unsaturated heterocycle optionally comprising at least one other non-nitrogen heteroatom; RO-CO- wherein the radical R is a C1-C4 alkyl radical optionally bearing at least one hydroxyl group; a cyclic, heterocyclic radical or a non-aromatic part of an aryl or heteroaryl radical may also be substituted with one or more oxo or thioxo groups; an aryl radical represents a mono or polycyclic group, condensed or not, comprising from 6 to 22 carbon atoms, and of which at least one ring is aromatic; preferably the aryl radical is a phenyl, biphenyl, naphthyl, indenyl, anthracenyl, or tetrahydronaphthyl; a diarylalkyl radical represents a group comprising, on the same carbon atom of an alkyl group, two identical or different aryl groups, such as diphenylmethyl or 1,1-diphenylethyl; a heteroaryl radical represents a mono- or polycyclic group, fused or otherwise, optionally cationic, comprising from 5 to 22 members, from 1 to 6 heteroatoms chosen from nitrogen, oxygen, sulfur and selenium, and at least one cycle is aromatic; preferably heteroaryl is selected from acridinyl, benzimidazolyl, benzobistriazolyl, benzopyrazolyl, benzopyridazinyle, benzoquinolyl, benzothiazolyl, benzotriazolyl, benzoxazolyl, pyridinyl, tetrazolyl, dihydrothiazolyl, imidazopyridinyl, imidazolyl, indolyl, isoquinolyl, naphthoimidazolyle, naphthooxazolyle, naphthopyrazolyle, oxadiazolyl, oxazolyl, oxazolopyridyl phenazinyl, phenoxazolyl, pyrazinyl, pyrazolyl, pyrilyl, pyrazoyltriazyl, pyridyl, pyridinoimidazolyl, pyrrolyl, quinolyl, tetrazolyl, thiadiazolyl, thiazolyl, thiazolopyridinyl, thiazoylimidazolyl, thiopyrylyl, triazolyl, xanthylyl and its ammonium salt; a diheteroarylalkyl radical represents a group comprising, on the same carbon atom of an alkyl group, two heteroaryl groups, which are identical or different, such as difurylmethyl, 1,1-difurylethyl, dipyrrolylmethyl and dithienylmethyl; a cyclic radical is a non-aromatic cycloalkyl radical, mono- or polycyclic, condensed or otherwise, containing from 5 to 22 carbon atoms, which can comprise from 1 to several unsaturations; particularly the cyclic radical is cyclohexyl; - A sterically hindered cyclic radical is a cyclic radical, aromatic or not, substituted or unsubstituted, hindered by steric effect or constraint, comprising from 6 to 14 members, which can be bridged, as sterically hindered radicals include bicyclo [1.1]. Butane, mesylates such as 1,3,5-trimethylphenyl, 1,3,5-triterbutylphenyl, 1,3,5-isobutylphenyl, 1,3,5-trimethylsilylphenyl and adamantyl; a heterocyclic radical or heterocycle is a non-aromatic mono- or polycyclic radical, condensed or not, containing from 5 to 22 members, comprising from 1 to 6 heteroatoms chosen from nitrogen, oxygen, sulfur and selenium; ; an alkyl radical is a C1-C16 hydrocarbon radical, linear or branched, preferably C1-C8; the optionally substituted expression attributed to the alkyl radical, that is to say that said alkyl radical may be substituted by one or more radicals chosen from i) hydroxyl, ii) C 1 -C 4 alkoxy, iii) acylamino, iv) amino optionally substituted by one or two identical or different C 1 -C 4 alkyl radicals, said alkyl radicals being capable of forming, with the nitrogen atom carrying them, a 5- to 7-membered heterocycle optionally comprising another heteroatom different from or different from nitrogen; v) or a quaternary ammonium group

  -N R'R "R" ', M for which R', R ", R" ', which are identical or different, represent a + hydrogen atom, or a C1-C4 alkyl group, or else -N R'R "R" 'form

  a heteroaryl such as imidazolium optionally substituted with a C 1 -C 4 alkyl group, and M represents the counterion of the corresponding organic acid, mineral acid or halide,

  an alkoxy radical is an alkyl-oxy or alkyl-O- radical for which the alkyl radical is a hydrocarbon radical, linear or branched, C1-C16, preferably C1-C8; an alkylthio radical is an alkyl-S- radical for which the alkyl radical is a hydrocarbon radical, linear or branched, C1-C16 preferably C1-C8; when the alkylthio group is optionally substituted, this implies that the alkyl group is optionally substituted as defined above;

  the boundaries delimiting the range of a range of values lie within this range of values;

  an organic or inorganic acid salt is more particularly chosen from a salt derived from i) hydrochloric acid HCl, ii) hydrobromic acid HBr, iii) sulfuric acid H 2 SO 4, iv) alkylsulphonic acids: Alk- S (O) 20H such as methylsulfonic acid and ethylsulfonic acid; v) arylsulfonic acids: Ar-S (O) 20H such as benzene sulfonic acid and toluene sulfonic acid; (vi) citric acid; vii) succinic acid; viii) tartaric acid; ix) lactic acid, x) alkoxysulfinic acids: Alk-O-S (O) OH such as methoxysulfinic acid and ethoxysulfinic acid; xi) aryloxysulfinic acids such as tolueneoxysulfinic acid and phenoxysulfinic acid; xii) phosphoric acid H3PO4; xiii) acetic acid CH3COOH; xiv) triflic acid CF3SO3H and xv) tetrafluoroboric acid HBF4;

  an anionic counterion is an anion or an anionic group associated with the cationic charge of the dye; more particularly the anionic counterion is selected from i) halides such as chloride, bromide; ii) nitrates; iii) sulphonates, including C1-C6 alkylsulphonates: Alk-S (O) 20- such as methylsulphonate or mesylate and ethylsulphonate; iv) arylsulfonates: Ar-S (O) 20-such as benzenesulfonate and toluenesulphonate or tosylate; v) citrate; vi) succinate; (vii) tartrate; viii) lactate; ix) alkylsulfites: Alk-O-S (O) O- such as methysulfite and ethylsulfite; x) arylsulfites: Ar-O-S (O) O- such as benzenesulphite and toluenesulphite; xi) alkyl sulphates: Alk-O-S (O) 20- such as methyl sulphate and ethyl sulphate; xii) arylsulfates: Ar-O-S (O) 20-, xiii) phosphate; (xiv) acetate; xv) triflate; and xvi) borates such as tetrafluoroborate.

  The thiol fluorescent dyes of formula (I) are compounds capable of absorbing in the UV or visible radiation at an Xabs wavelength of between 250 and 800 nm and capable of reemitting in the visible range at a wavelength. Xem emission between 400 and 800 nm. Preferably thiol fluorescent compounds of the invention are dyes capable of absorbing in the visible Xabs between 400 and 800 nm and reemitting in the visible Xem between 400 and 800 nm. More preferably, thiols fluorescent dyes having a heterocyclic group of formula (I) are dyes capable of absorbing at an Xabs between 420 nm and 550 nm and reemitting in the visible at an Xem of between 470 and 600 nm.

  The fluorescent compounds of the invention contain a SY function which may be in the covalent -S-Y or ion -S-Y + form depending on the nature of Y and the pH of the medium. One particular embodiment relates to thiols fluorescent dyes having a heterocyclic group of formula (I) with SY function where Y represents a hydrogen atom, or an alkali metal. Advantageously, Y represents a hydrogen atom.

  According to another particular embodiment of the invention, in formula (I) above, Y is a protective group known to those skilled in the art such as those described in the books Protective Groups in Organic Synthesis, TW Greene, John Willey & Sons ed., NY, 1981, pp.193-217; Protecting Groups, P. Kocienski, Thieme, 3rd ed., 2005, chap. 5. Particularly when Y is a protecting group for the thiol function, Y is selected from the following radicals: (C 1 -C 4) alkylcarbonyl; (C1-C4) alkylthiocarbonyl; (C1-C4) alkoxycarbonyl; (C 1 -C 4) alkoxythiocarbonyl; C 1 -C 4 alkylthio thiocarbonyl; ^ (di) (C1-C4) (alkyl) aminocarbonyl; ^ (di) (C1-C4) (alkyl) aminothiocarbonyl; arylcarbonyl as phenylcarbonyl; aryloxycarbonyl; aryl (C1-C4) alkoxycarbonyl; (di) (C1-C4) (alkyl) aminocarbonyl as dimethylaminocarbonyl; (C 1 -C 4) (alkyl) arylaminocarbonyl; carboxy; ^ S03; M + with M + representing an alkali metal such as sodium or potassium, or else M 'of the formula (I) and M + are absent; optionally substituted aryl such as phenyl, dibenzosuberyl, or 1,3,5-cycloheptatrienyl, optionally substituted heteroaryl; including in particular cationic or non-cationic heteroaryl, comprising from 1 to 4 following heteroatoms: i) monocyclic with 5, 6 or 7 members such as furanyl or furyl, pyrrolyl or pyrryl, thiophenyl or thienyl, pyrazolyl, oxazolyl, oxazolium, isoxazolyl, isoxazolium thiazolyl, thiazolium, isothiazolyl, isothiazolium, 1,2,4-triazolyl, 1,2,4-triazolium, 1,2,3-triazolyl, 1,2,3-triazolium, 1,2,4-oxazolyl, 1 2,4-oxazolium 1,2,4-thiadiazolyl 1,2,4-thiadiazolium pyrylium thiopyridyl pyridinium pyrimidinyl pyrimidinium pyrazinyl pyrazinium pyridazinyl pyridazinium triazinyl triazinium tetrazinyl tetrazinium azepine azepinium, oxazepinyl, oxazepinium, thiepinyl, thiepinium, imidazolyl, imidazolium; ii) 8 to 11-membered bicyclic compounds such as indolyl, indolinium, benzoimidazolyl, benzoimidazolium, benzoxazolyl, benzoxazolium, dihydrobenzoxazolinyl, benzothiazolyl, benzothiazolium, pyridoimidazolyl, pyridoimidazolium, thienocycloheptadienyl, these mono or bicyclic groups being optionally substituted by one or more groups such as C 1 -C 4) alkyl as methyl, or polyhalo (C 1 -C 4) alkyl as trifluoromethyl; iii) or tricyclic ABC according to: wherein the two rings A, C optionally comprise a heteroatom, and the ring B is a 5-, 6- or 7-membered particularly 6-membered ring and contains at least one heteroatom such as pyperidyl, pyranyl ; optionally substituted heterocycloalkyl, optionally cationic, the heterocycloalkyl represents in particular a saturated or partially saturated monocyclic group with 5, 6 or 7 members comprising 1 to 4 heteroatoms selected from oxygen, sulfur and nitrogen, such as di / tetrahydrofuranyl; , di / tetrahydrothiophenyl, di / tetrahydropyrrolyl, di / tetrahydropyranyl, di / tetra / hexahydrothiopyranyl, dihydropyridyl, piperazinyl, piperidinyl, tetramethylpiperidinyl, morpholinyl, di / tetra / hexahydroazepinyl, di / tetrahydropyrimidinyl these groups being optionally substituted with one or more groups such as C1-C4) alkyl, oxo or thioxo; or the heterocycle represents the following group: R '\ R'g R, "N i (CR'eR'f) v R'd - An in which R', R'd, R'e, R'f, R'g and R '", which are identical or different, represent a hydrogen atom or a (C1-C4) alkyl group, or else two R'g groups with R'", and / or R'e with R'f form an oxo or thioxo group, or else R'g with R'e together form a cycloalkyl, and v represents an integer inclusive between 1 and 3, preferentially R 'to R' "represent a hydrogen atom; and An represents a counterion; isothiouronium -C (NR 'R'd) = N + R'eR'f; An with R ', R'd, R'e and R'f, identical or different, represent a hydrogen atom or a (C 1 -C 4) alkyl group; preferentially R 'to R' f represent a hydrogen atom; and An represents a counterion; isothiourea -C (NR 'R'd) = NR'e; with R'd and R'e as defined above; optionally substituted di (aryl) (C 1 -C 4) alkyl, such as 9-anthracenylmethyl, phenylmethyl or diphenylmethyl, optionally substituted by one or more groups chosen in particular from (C 1 -C 4) alkyl, (C 1 -C 4) alkoxy, such as methoxy, hydroxy, (C1-C4) alkylcarbonyl, (di) (C1-C4) (alkyl) amino such as dimethylamino; optionally substituted heteroaryl (C 1 -C 4) alkyl, the heteroaryl group is in particular, cationic or non-monocyclic, comprising 5 or 6 members and 1 to 4 heteroatoms chosen from nitrogen, oxygen and sulfur; , such as pyrrolyl, furanyl, thiophenyl, pyridyl, pyridyl N-oxide such as 4-pyridyl or 2-pyridyl-N-oxide, pyrylium, pyridinium, triazinyl, optionally substituted with one or more group such as alkyl particularly methyl preferably (di) heteroaryl (C 1 -C 4) alkyl is (di) heteroarylmethyl or (di) heteroarylethyl; CR'R 2 R 3 with R ', R 2 and R 3, which may be identical or different, representing a halogen atom or a group chosen from: - (C 1 -C 4) alkyl; - (C1-C4) alkoxy; optionally substituted aryl such as phenyl optionally substituted by one or more groups such as (C 1 -C 4) alkyl, (C 1 -C 4) alkoxy, hydroxy; - optionally substituted heteroaryl such as thiophenyl, furanyl, pyrrolyl, pyranyl, pyridyl, optionally substituted with a (C1-C4) alkyl group; -P (Z ') R''R'2R'3 with R'1, and R'2 identical or different represent a hydroxyl group, (C1-C4) alkoxy or alkyl, R'3 represents a hydroxyl group or ( C 1 -C 4) alkoxy, and Z 'represents an oxygen or sulfur atom; sterically hindered cyclic such as adamantyl group; and optionally substituted (C 1 -C 4) alkoxyalkyl such as methoxymethyl (MOM), ethoxyethyl (EOM) and isobutoxymethyl.

  According to a particular embodiment, the protected heterocyclic thiol protected fluorescent dyes of formula (I) comprise a cationic aromatic 5- or 6-membered monocyclic moiety Y i) heteroaryl comprising from 1 to 4 heteroatoms selected from oxygen, sulfur and nitrogen, such as oxazolium, isoxazolium, thiazolium, isothiazolium, 1,2,4-triazolium, 1,2,3-triazolium, 1,2,4-oxazolium, 1,2,4-thiadiazolium, pyrylium, pyridinium, pyrimidinium, pyrazinyl, pyrazinium, pyridazinium, triazinium, tetrazinium, oxazepinium, thiepinyl, thiepinium, imidazolium; ii) cationic 8 to 11-membered bicyclic heteroaryl such as indolinium, benzoimidazolium, benzoxazolium, benzothiazolium, these mono or bicyclic heteroaryl groups being optionally substituted with one or more groups such as alkyl as methyl, or polyhalo (C 1 -C 4) alkyl as trifluoromethyl; iii) or heterocyclic according to: R '\ N + N R'd An in which R' and R'd, identical or different, represent a hydrogen atom or a (C 1 -C 4) alkyl group; preferentially R 'to R'd represent a (C 1 -C 4) alkyl group such as methyl; and An represents a counterion.

  Especially Y represents a group chosen from oxazolium, isoxazolium, thiazolium, isothiazolium, 1,2,4-triazolium, 1,2,3-triazolium, 1,2,4-oxazolium, 1,2,4-thiadiazolium, pyrylium, pyridinium , pyrimidinium, pyrazinium, pyridazinium, triazinium and imidazolium, benzoimidazolium, benzoxazolium, benzothiazolium, these groups being optionally substituted by one or more (C1-C4) alkyl groups including methyl. In particular Y represents an alkali metal or a protective group such as: - (C 1 -C 4) alkylcarbonyl such as methylcarbonyl or ethylcarbonyl; arylcarbonyl, such as phenylcarbonyl; - (C1-C4) alkoxycarbonyl; aryloxycarbonyl; -aryl (C1-C4) alkoxycarbonyl; - (di) (C1-C4) (alkyl) aminocarbonyl such as dimethylaminocarbonyl; - (C1-C4) (alkyl) arylaminocarbonyl; optionally substituted aryl such as phenyl; monocyclic 5,6-membered heteroaryl such as imidazolyl or cationic 5-6 membered monocyclic heteroaryl, such as pyrylium, pyridinium, pyrimidinium, pyrazinium, pyridazinium, triazinium, imidazolium; these groups being optionally substituted by one or more, identical or different, (C 1 -C 4) alkyl groups such as methyl; - 8 to 11-membered cationic bicyclic heteroaryl such as benzoimidazolium, or benzoxazolium; these groups being optionally substituted by one or more, identical or different, (C 1 -C 4) alkyl groups such as methyl; cationic heterocycle of the following formula: ## STR5 ## An; • isothiourea -C (NH2) = NH; • S03, M +. According to one particular embodiment of the invention, the dyes of the invention belong to the formula (la) which has the ethylene group connecting the pyridinium part to the phenyl in the ortho or para position or in the 4-4 ', 2-2 positions. ', 4-2', or 2-4 ': with formulas (la): where e represents a saturated or unsaturated heterocyclic group; monocyclic compound comprising 5 to 7 members and having 1 or two heteroatoms selected from nitrogen, oxygen or sulfur, particularly the heteroatom is a nitrogen atom; in particular, the heterocycle is selected from pyrazolyl, piperazinyl, piperidinyl, morpholinyl, and imidazolyl; - Rg, R'g, Rh and R'h, identical or different, represent a hydrogen atom or a (C 1 -C 4) alkyl group especially the groups Rh and R'h are ortho pyridinium and represent a (C 1 -C 4) alkyl group and R 8 and R '8 represent a hydrogen atom; Ta represents a covalent bond a, or a group selected from: ## EQU1 ## where R (R) u (C) O (C) O (C) O (C) and wherein R, R + (R) (R), where R, R being the same or different, representing a hydrogen atom, a C1-C4 alkyl group; particularly Ta represents a bond at 25 - m and n, which are identical or different, represent an integer inclusive between 0 and 6 with m + n represents an integer inclusive between 2 and 6; preferentially m + n is an integer equal to 2; M 'representing an anionic counterion; and Y is as defined above; It being understood that: the function SY can be in the covalent -SY or ionic form -S Y + 5 depending on the nature of Y and the pH of the medium and - when the compound of formula (I) contains other parts cationic, it is associated with one or more anionic counter-ions making it possible to reach the electroneutrality of formula (I).

  By way of example of thiol fluorescent dyes, mention may be made in particular of the following compounds: ## STR1 ## in which: ## STR1 ## / CN / CN / CNS / CNS / CN / CNS / CN / CNS / CNS / CNS / CNS / CNS / CNS / CNS / CNS '\ N + M' ~ / -NJNOH 9 10 ON \ N_ CN \ / \ V) = - N 'N ~ NJ ~ r 2M' M '11 12 CN / \ 2M' / / \ NOS \ 13 With M 'representing an anionic counterion.

  The protected thiol dyes of formulas (I ') and (I ") can be synthesized in two steps: the first step of preparing unprotected thiol dye (IH) according to the methods known to those skilled in the art as per Thiols and organic sulphides, Thiocyanates and Isothiocyanates, organic, Ullmann's Encyclopedia, Wiley-VCH, Weinheim, 2005. And the second step of protecting the thiol function according to conventional methods known to those skilled in the art to lead to protected thiol dyes. of formula (I ') and (I "). By way of example, to protect the thiol function of the thiol dye, the methods of Protectin Groups in Organic Synthesis, T.W. Greene, John Willey & Sons, Ed., NY, 1981, pp.193-217; Protecting Groups, P. Kocienski, Thieme, 3rd ed., 2005, chap. 5.

  We can illustrate this method by the method consisting of i) generating thiol fluorescent dyes of formula (IH) by reduction of a heterocyclic, two-chromophore fluorescent dye carrying a disulfide function -SS-such as 5 and ii) to be protected according to conventional methods, said thiol function of (1H) with the reagent 7 Y'R to access the protected thiol fluorescent dyes of formula (I '). The thiol compound (1H) may also be metallized with an alkali metal or alkaline earth metal Met * to yield the thiolate fluorescent dye of formula (I "). + M 'M' / Ta N - (CRI R2), (CR3R4) n (CR3R4) (CRi R2) m ù Ri 7 Y'R - Y'H R'h iTa Met * metallation R. where N ~ (CR ~ R2) m ~ (CR3R4) n (1a) M 'with Y' representing a protecting group of thiol function; Met * representing an alkali metal or an alkaline earth metal, particularly sodium or potassium,

  It being understood that when the metal is an alkaline earth metal 2 thiolate-functional chromophores-S- may be associated with 1 Metal2 +. with R 1, R 2, R 3, R 4, R 6, R 6, Rh, R 1, R 2, R ', m, n, het and M' are as defined above; Y 'represents a protecting group of thiol function; and R represents a leaving group nucleofuge, such as, for example, mesylate, tosylate, triflate or halide.

  According to another possibility, a thiol compound protected by a protecting group Y 'as defined previously prepared can be reacted according to one of the procedures described in the works cited above, said protected thiol compound comprising at least one nucleophilic function with a sufficient amount , preferably equimolar, of a "reactive fluorescent chromophore" or of a compound comprising such a "reactive fluorescent chromophore" j. In other words, it comprises an electrophilic function to form a covalent bond E as can be schematized below in the preparation of fluorescent dyes of formula (I "'): Sa1 het N with R1, R2, R3, R4 , Rg, R'g, Rh, R'h, R, R ', m, n, het, Y' and M 'are as defined above; u represents a nucleophilic group; E represents an electrophilic group; and E the bond generated after nucleophilic attack on the electrophile.

  By way of example, the covalent bonds E that can be generated are listed in the table below from the condensation of electrophiles with nucleophiles: Electrophiles E Nucleophiles Wu Covalent bonds E Activated esters * Amines Carboxamides Acyl azides * * Amines Carboxamides Acyl halides Amines Carboxamides Acyl halides Alcohols Esters Acyl cyanides Alcohols Esters Acyl cyanides Amines Carboxamides Alkyl halides Amines Alkylamines Alkali halides Carboxylic acids Esters Alkali halides Thiols Thioesters 5 Halides alkyl Alcohols Ethers Sulphonic acids and their Thiols Thioethers salts Sulphonic acids and their carboxylic acids Salt esters Sulphonic acids and their alcohols Ethers salts Anhydrides Alcohols Esters Anhydrides Amines Carboxamides Aryl halides Thiols Thioethers Aryl halides Amines Arylamines Aziridines Thiols Thioethers Carboxylic acids Amines Carb oxamides Carboxylic Acids Alcohols Esters Carbodiimides Carboxylic Acids N-acyl ureas or anhydrides Diazoalkanes Carboxylic Acids Esters Epoxides Thiols Thioethers Haloacetamides Thiols Thioethers Esters imides Amines Amidines Isocyanates Amines Ureas Isocyanates Alcohols Urethanes Isothiocyanates Amines Thioureas Maleimides Thiols Thioethers Sulphonic esters Amines Alkylamines Sulphonic esters Thiols Thioethers Esters sulfonic Acids carboxylic esters Esters Sulphonic esters Alcohols Ethers Sulfonyl halides Amines Sulfonamides * Activated esters of the general formula ûCO-Part with Part representing a leaving group such as oxysuccinimidyl, oxybenzotriazolyl, optionally substituted aryloxy;

  ** Acyl azides can rearrange to give isocyanates.

  An alternative to this method is to use a fluorescent chromophore having an electrophilic acrylate function (-OCO-C = C-) on which an addition reaction is carried out which will generate an L bond. It will also be possible to use a thiol reagent Y'- SH comprising a group Y 'as defined above, the nucleophilic function SH of which can react on the carbon atom alpha to the halogen atom carried by the fluorescent chromophore to give the protected thiol fluorescent dye of formula (I') ): Rh M 'L1HS-Y' (CR1R2), Ta (CR3R4) ~ Hal - HHaI (I ') with R1, R2, R3, R4, Rg, R'g, Rh, R'h, Ta, R , R ', m, n, het, Y', (I ') and M' are as defined above, and Hal represents a nucleofugal halogen atom such as bromine, iodine or chlorine.

  More particularly, it will be possible to substitute a nucleofugal leaving group with a thiourea group (S = C (NRR) NRR) to generate the isothiouroniums. For example, if the thiourea group is a thioimidazolinium ([3), the reaction scheme is as follows: M '. ^ / Hal L. jNùR'd Lm An R'cN Rh M' Î An R'a R'c, SH with R ', R'd, Rg, R'g, Rh, R'h, R, R', m, n, het, Hal, An- and M 'are as defined above. According to another variant it is possible to generate an imidazoline intermediate from the halide comprising the fluorescent chromophore (a ') and a thioimidazoline (b') to conduct after alkylation with a reagent R-Gp with R representing an alkyl group and Gp a leaving group such as a halogen such as chlorine, bromine, iodine, or a group mesylate or tosylate.

  N --''- (/ Hal INM 'R'0, SH R'O \\ N alkylation (R'd-Gp) R'ON NM' NI Gp R'd A variant is to use in place of the halide comprising the fluorescent chromophore; a chromophore comprising another type of nucleofuge such as tosylate, mesylate.

  According to another possibility, certain protected thiol fluorescent dyes (I ") can be obtained by reacting a protected thiol compound with a compound carrying two carboxylic acid functional groups activated by conventional methods (for example reaction with a carbodiimide or with chloride The resulting product is then reacted with a fluorescent chromophore bearing a nucleophilic function, for example of the primary or secondary amine type, or of the aliphatic alcohol type Rh (CR) R2 + E- (CR3R4) n SY'Lcj with R1, R2, R3, R4, Rg, R'g, Rh, R'h, R, R ', het, Ta, Y', m, n, M ', E, Wu and (I "') as defined above. Another variant is to use a thiolactone as described below: Y'R-Y'H (B) metallation (\ H2) 3 sY 'A variant of synthesis is to combine the first channel with the previous one ie From two equivalents of the nucleophilic reagent with a disulfide-disulfide reagent it is possible to generate after condensation the dichromophoric disulfide product (A '), the latter being able to undergo a reduction to form the heterocyclic fluorescent thiol dye which in turn can either be protect to form the protected thiol fluorescent dye (I "') or be metallized with an alkali metal to yield the metallocyclic heterocyclic thiol fluorescent dye (I"' Metal) YMMN `(CR, R2) n, ~ (CR3R4) n ( CR3R44) (CR1R2) m (A ') reduction According to another possibility, protected thiol fluorescent dyes of formula (I "') can be obtained by reaction of a compound comprising a thiol group protected by a group Y ', and a previously activated hydroxy group leaving nucleofugal group j, such as mesylate, tosylate, triflate or halide with a styrylpyridine chromophore jj. (CR, R2) m fu + rEu (CR3R4) ~ Si (CR3R4) ~ rEi With R1, R2, R3, R4, Rg, R'g, Rh, R'h, R, R ', Het , Ta, Y ', m, n, (I "') and E are as defined above.

  By way of example, a compound containing a protected thiol group contains a leaving group R, such as, for example, mesylate, tosylate, or triflate, which can undergo the nucleophilic attack of the amine carried by the styryl fluorescent chromophore: Another alternative comes from the use of halides as leaving group nucleofuge on a thiol compound which may be substituted by a primary amine function, for example carried by a styryl fluorescent chromophore: Rh

  According to another possibility, the thiol fluorescent dyes of formula (I) according to the invention can be obtained by reaction of a compound comprising a thiol group Y as defined above and an electrophilic group Lfl with a pyridinium compound comprising a nucleophilic group. For example, an aldehyde, ketone or thioaldehyde, thioketone may be condensed when G 'represents an oxygen atom or sulfur with an activated methylene such as alkylpyridinium to generate an ethylene> C = C bond <. This reaction is commonly known as Knoevenagel condensation. Activated methylenes are understood to mean those which preferably contain, in the 2- or 4-position of the pyridinium group, a methylene group R 1 -CH 2 -: Rh + h M iTa 2, SY (1) R'i R 1 (CRIR 2) m (CR 3 R 4) n -H 2 G 'in with R 1, R 2, R 3, R 4, R a, R b, R 6, R' 8, Rh, R ', R', R ', Ta, Het , m, n, Y and M 'as defined above and G' representing an oxygen atom, sulfur or a group N (R) with R representing a hydrogen atom or a group (C 1 -C 4) alkyl .

  Reference may be made to Advanced Organic Chemistry, Reactions, Mechanisms and Structures, J. March, 4th Ed, John Willey & Sons, 1992 or T. W.

  Greene Protective Groups in Organic Synthesis, for more details on the operating conditions used for the processes mentioned above. The thiol fluorescent dyes formed can be converted to Y-protected thiols fluorescent dyes by the protection of thiols using conventional protecting groups. The thiol fluorescent dyes are metallated using also conventional methods known to those skilled in the art such as those described in Advanced Organic Chemistry, Reactions, Mechanisms and Structures, J. March, 4th Ed, John Willey & Sons, NY, 1992. Protected thiol dyes may be deprotected by conventional routes such as those described in Protective Groups in Organic Synthesis, TW Greene, John Willey & Sons ed., NY, 1981; Protecting Groups, P. Kocienski, Thieme, 3rd ed., 2005. The starting reagents are commercial or accessible by conventional methods known to those skilled in the art. For example it is possible to synthesize the reagent 5 from 2 equivalents of pyridine derivative 1 and one equivalent of disulfide reagent comprising two leaving groups Gp, to lead to dipyridinium disulfide salt 3 which can be condensed in turn with two equivalents of aryl compound with an aldehyde / thioaldehyde group 4 to yield 5. G 'Gp (CRR 2) m (CR 3 R 4) q Gp (CRR 2) m (CR 3 R 4), SR, h 2 3 Knoevenagel - 2 H2G with Gp representing a group hence nucleofuge, such as, for example, mesylate, tosylate, triflate or halide. The counter ions Gp- of the compounds 5, above may be replaced by counterions M 'of other types from methods known to those skilled in the art including ion exchange resin.

  Reference may be made to Advanced Organic Chemistry, Reactions, Mechanisms and Structures, J. March, 4th Ed, John Willey & Sons, 1992 or TW Greene Protective Groups in Organic Synthesis, for further details on operating conditions. for the processes mentioned above. The thiol fluorescent dyes formed can be converted to Y-protected thiols fluorescent dyes by the protection of thiols using conventional protecting groups. The thiol fluorescent dyes are metallated using also conventional methods known to those skilled in the art such as those described in Advanced Organic Chemistry, Reactions, Mechanisms and Structures, J. March, 4th Ed, John Willey & Sons, NY, 1992. Protected thiol dyes may be deprotected by conventional routes such as those described in Protective Groups in Organic Synthesis, TW Greene, John Willey & Sons ed., NY, 1981; Protecting Groups, P. Kocienski, Thieme, 3rd ed., 2005.

  The composition of the invention contains at least one thiol fluorescent dye of formula (I). In addition to the presence of at least one fluorescent dye of formula (I), the composition of the invention may also contain a reducing agent. This reducing agent may be chosen from thiols, for example cysteine, homocysteine, thiolactic acid, the salts of these thiols, phosphines, bisulfite, sulphites, thioglycolic acid and its esters, especially the glycerol monothioglycolate, and thioglycerol. This reducing agent may also be chosen from G Gp iTa / Ta pN (CRR2), (CR3R4) n CR3R4) n (CR R2) n, 3 borohydrides and their derivatives, such as, for example, the salts of borohydride, cyanoborohydride, triacetoxyborohydride, trimethoxyborohydride: sodium, lithium, potassium, calcium, quaternary ammonium salts (tetramethylammonium, tetraethylammonium, tetra-n-butylammonium, benzyltriethylammonium), catecholborane The dyeing composition useful in the invention generally contains a amount of thiol fluorescent dye of formula (I) between 0.001% and 50% relative to the total weight of the composition, this amount is preferably between 0.005% and 20% by weight and even more preferably between 0.01% and 5% by weight relative to the total weight of the composition The dyeing composition may further contain additional direct dyes These direct dyes are, for example, chosen from the following direct dyes: Neutral, acid or cationic neutral benzene dyes, neutral, acid or cationic azo direct dyes, tetraazapentamethine dyes, neutral or acidic or cationic quinone dyes and in particular neutral anthraquinone dyes, azine direct dyes, triarylmethane direct dyes, indoamine direct dyes and natural direct dyes. Among the natural direct dyes that may be mentioned are lawsone, juglone, alizarin, purpurin, carminic acid, kermesic acid, purpurogalline, protocatechaldehyde, indigo, isatin, curcumin, spinulosin, apigenidine. It is also possible to use the extracts or decoctions containing these natural dyes, and in particular poultices or extracts made from henna. The dye composition may contain one or more oxidation bases and / or one or more couplers conventionally used for dyeing keratinous fibers. Among the oxidation bases, mention may be made of para-phenylenediamines, bis-phenylalkylenediamines, para-aminophenols, bis-para-aminophenols, ortho-aminophenols, heterocyclic bases and their addition salts. Among these couplers, mention may especially be made of meta-phenylenediamines, meta-aminophenols, meta-diphenols, naphthalenic couplers, heterocyclic couplers and their addition salts. The coupler or couplers are each generally present in an amount of between 0.001 and 10% by weight of the total weight of the dye composition, preferably between 0.005 and 6%.

  The oxidation base (s) present in the dyeing composition are in general each present in an amount of between 0.001% and 10% by weight relative to the total weight of the dyeing composition, preferably between 0.005% and 6% by weight.

  In general, the addition salts of the oxidation bases and couplers that can be used in the context of the invention are chosen especially from the addition salts with an acid such as hydrochlorides, hydrobromides, sulphates, citrates, succinates, tartrates, lactates, tosylates, benzenesulfonates, phosphates and acetates and addition salts with a base such as alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, ammonia, amines or alkanolamines. The medium suitable for dyeing, also called dyeing medium, is a cosmetic medium generally consisting of water or a mixture of water and at least one organic solvent. As organic solvent, there may be mentioned for example lower alkanols C1-C4, such as ethanol and isopropanol; polyols and polyol ethers such as 2-butoxyethanol, propylene glycol, propylene glycol monomethyl ether, diethylene glycol monoethyl ether and monomethyl ether, as well as aromatic alcohols such as benzyl alcohol or phenoxyethanol, and mixtures thereof. The solvents when present are preferably present in proportions preferably of between 1 and 40% by weight approximately relative to the total weight of the dye composition, and even more preferably between 5 and 30% by weight approximately.

  According to one variant, the invention contains a reducing agent capable of reducing the disulfide bonds of keratin. This reducing agent is as defined above. The dye composition may also contain various adjuvants conventionally used in compositions for dyeing hair, such as anionic, cationic, nonionic, amphoteric, zwitterionic surfactants or mixtures thereof, anionic, cationic, nonionic, amphoteric and zwitterionic polymers. or mixtures thereof, inorganic or organic thickeners, and in particular anionic, cationic, nonionic and amphoteric polymeric associative thickeners, antioxidants, penetrating agents, sequestering agents, perfumes, buffers, dispersing agents, conditioning agents such as, for example, volatile or non-volatile silicones, modified or otherwise, such as aminosilicones, film-forming agents, ceramides, preserving agents, opacifying agents, conductive polymers. The adjuvants above are generally present in an amount for each of them between 0.01 and 20% by weight relative to the weight of the composition. Of course, one skilled in the art will take care to choose this or these optional additional compounds in such a way that the advantageous properties intrinsically attached to the dyeing composition according to the invention are not, or not substantially, impaired by the or the additions envisaged. The pH of the dyeing composition is generally between 3 and 14 approximately, and preferably between 5 and 11 approximately. It can be adjusted to the desired value by means of acidifying or alkalizing agents usually used for dyeing keratin fibers or else using conventional buffer systems. Among the acidifying agents, mention may be made, by way of example, of mineral or organic acids such as hydrochloric acid, orthophosphoric acid, sulfuric acid, carboxylic acids such as acetic acid, tartaric acid, citric acid, lactic acid, sulphonic acids. Among the alkalinizing agents that may be mentioned, by way of example, are ammonia, alkaline carbonates, alkanolamines such as mono-, di- and triethanolamines and their derivatives, sodium or potassium hydroxides and following formula (y): R 1 R a 2 / N Wa N Ra 4 a 3 (y) in which Wa is a propylene residue optionally substituted with a hydroxyl group or a C 1 -C 4 alkyl radical; Ra1, Ra2, Ra3 and Ra4, which may be identical or different, represent a hydrogen atom, a C1-C4 alkyl radical or a C1-C4 hydroxyalkyl radical.

  The dye composition may be in various forms, such as in the form of liquid, cream, gel, or in any other form suitable for dyeing keratinous fibers, and in particular hair.

  According to a particular embodiment in the process of the invention, a reducing agent may be applied pre-treatment before application of the composition containing at least one heterocyclic thiol fluorescent dye of formula (I). This reducing agent may be chosen from thiols, for example cysteine, homocysteine, thiolactic acid, the salts of these thiols, phosphines, bisulfite, sulphites, thioglycolic acid and its esters, especially the glycerol monothioglycolate, and thioglycerol. This reducing agent may also be chosen from borohydrides and their derivatives, such as, for example, borohydride, cyanoborohydride, triacetoxyborohydride or trimethoxyborohydride salts: sodium, lithium, potassium, calcium, quaternary ammonium salts (tetramethylammonium, tetraethylammonium, tetra butylammonium, benzyltriethylammonium); catecholborane. This pretreatment may be of short duration, in particular from 0.1 second to 30 minutes, preferably from 1 minute to 15 minutes with a reducing agent as mentioned above. According to another method, the composition comprising at least one thiol fluorescent dye of formula (I) also contains at least one reducing agent as defined above. This composition is then applied to the hair. When the thiol fluorescent dye of formula (I) comprises a group Y protecting the thiol function, the process of the invention may be preceded by a deprotection step aimed at rendering the SH function in situ. By way of example, it is possible to deprotect the SY function with the protective group by adjusting the pH as follows: Y: alkylcarbonyl deprotection protecting group, pH> 9 arylcarbonyl, pH> 9 alkoxycarbonyl, pH> 9 aryloxycarbonyl, pH> 9 arylalkoxycarbonyl pH> 9 (di) (alkyl) aminocarbonyl, pH> 9 (alkyl) arylaminocarbonyl pH> 9 aryl optionally substituted such pH> 9 as phenyl, monocyclic heteroaryl with 5, 6 or 7 pH> 9 members such as oxazolium; 8 to 11-membered bicyclic heteroaryl pH> 9-membered such as benzoimidazolium, or benzoxazolium The deprotection step can also be carried out in the course of a hair pretreatment step such as, for example, the reducing pretreatment of the hair. According to one variant, the reducing agent is added to the dyeing composition containing at least one thiol fluorescent dye of formula (I) at the time of use. According to another variant, the reducing agent is applied in post-treatment. after the application of the composition containing at least one thiol fluorescent dye (I). The duration of the post-treatment with the reducing agent may be short, for example from 0.1 second to 30 minutes, preferably from 1 minute to 15 minutes, with a reducing agent as described above. According to a particular embodiment, the reducing agent is a thiol or borohydride type agent as described above. A particular embodiment of the invention relates to a method in which the thiol fluorescent dye can be applied directly to hair without reducing agents, free of pre- or post-treatment reducers. A treatment with an oxidizing agent may optionally be associated. Any type of conventional oxidizing agent may be used in the art. Thus, it may be chosen from hydrogen peroxide, urea peroxide, alkali metal bromates, persalts such as perborates and persulphates, as well as the enzymes among which may be mentioned peroxidases, oxides, 2-electron reductases such as uricases and 4-electron oxygenases such as laccases. The use of hydrogen peroxide is particularly preferred. This oxidizing agent may be applied to the fibers before or after the application of the composition containing at least one thiol fluorescent dye of formula (I). The application of the dye composition according to the invention is generally carried out at room temperature. It can however be carried out at temperatures ranging from 20 to 180 C.

  The invention also relates to a multi-compartment device or "kit" of dyeing in which a first compartment contains a dye composition comprising at least one thiol fluorescent dye of formula (I) and a second compartment contains a reducing agent capable of reducing the disulfide functions of keratin materials.

  One of these compartments may further contain one or more other dyes of direct dye type or oxidation dye. It also relates to a multi-compartment device in which a first compartment contains a dye composition comprising at least one thiol fluorescent dye of formula (I); a second compartment contains a reducing agent capable of reducing the disulfide bond of the keratin materials; a third compartment contains an oxidizing agent. Alternatively, the dyeing device contains a first compartment containing a dye composition which comprises at least one protected thiol fluorescent dye of formula (I) and a second compartment containing an agent capable of deprotecting the protected thiol to release the thiol. Each of the devices mentioned above can be equipped with a means for delivering the desired mixture onto the hair, for example such as the devices described in patent FR 2 586 913.

  The examples which follow serve to illustrate the invention without, however, being limiting in nature. The thiol fluorescent dyes of the examples below have been fully characterized by conventional spectroscopic and spectrometric methods.

  EXAMPLES SYNTHETIC EXAMPLE Synthesis of 4 - [(E) -2- (4-pyrrolidin-1-ylphenyl) vinyl] -1- (2-sulfanylethyl) pyridinium methanesulfonate [1] o - 11, o SH SO [1] Synthesis Scheme ## STR1 ## of 2,2'-dithiodiethanol dimethanesulfonate disulfanediyldiethane-2,1-diyl and 14.44 g of triethylamine (TEA) are diluted in 100 ml of ethyl acetate, at 0 ° C, 16.35 g of methanesulfonyl diluted in 35 ml of ethyl acetate are added dropwise to the reaction medium with rapid stirring 7.22 g of triethylamine are introduced, the stirring is continued at ambient temperature for 4 h 30. methanesulfonyl are added dropwise at 15 ° C., the stirring is then maintained at room temperature for 17 h, the precipitate is filtered and washed with 3 times 50 ml of ethyl acetate. extracted with 100 ml of ice water, 100 ml of water, 3 times 50 ml of a saturated solution of sodium hydrogencarbonate (NaHCO3), twice with 20 ml of saturated sodium chloride solution (NaCl), then dried over anhydrous sodium sulphate (Na2SO4). The ethyl acetate is evaporated, and 17.49 g of pale yellow translucent oil is collected and stored at -25 C. Analyzes indicate that the product is compliant and pure.

  Step 2: Synthesis of 1,1 '- (disulfanediyldiethane-2,1-diyl) bis (4-methylpyridinium) Dimethhanesulfonate

  3.51 g of 4 picoline and 5 g of disulfanediyldiethane-2,1-diyl dimethanesulphonate are diluted in 5 ml of N-methylpyrrolidinone (NMP) and then heated at 80 ° C. with stirring for 2 h. Stirring is maintained at room temperature for 17 hours. The reaction medium is supplemented with 50 ml of ethyl acetate, then filtered, washed with 3 times 100 ml of ethyl acetate (AcOEt), and dried under vacuum under P205. 7.29 g of brown powder are collected. The analyzes indicate that the product is compliant and pure.

  Step 3: Synthesis of 1,1 '- (disulfanediyldiethane-2,1-diyl) bis {4 - [(E) -2- (4-pyrrolidin-1-ylphenyl) vinyl] pyridinium dimethane sulfonate [a]

  3.42 g of 4- (1-pyrrolidino) benzaldehyde, 10 ml of isopropanol, and 1.69 ml of pyrrolidine are mixed with stirring for 10 minutes. 1.18 mL of acetic acid is added and the mixture is stirred at room temperature for 20 minutes. 5 g of 1,1 '- (disulfanediyldiethane-2,1-diyl) bis (4-methylpyridinium) di-methanesulphonate in suspension in 7 ml of isopropanol and 2 ml of methanol are added. The reaction mixture is stirred for 24h at room temperature. The precipitate obtained is filtered, washed with 100 mL of acetone and then dried. 7.24 g of powder are collected. The analyzes indicate that the product is compliant and pure.

  1H NMR (400 MHz, MeOH-d4) 2.03 - 2.06 (m, 8H), 2.71 (s, 6H), 3.3 - 3.4 (m, 12H), 4.7 (t, 4H), 6.6 (d, 4H), 6.99 (d, 2H), 7.57 (d, 4H), 7.8 (d, 2H), 7.93 (d, 4H), 8.53 (d, 4H).

Step 4: Synthesis of 4 - [(E) -2- (4-pyrrolidin-1-ylphenyl) vinyl] -1- (2-sulfanylethyl) pyridinium salt [1]

  81 mg of the compound [la] are dissolved in 10 ml of water / ethanol mixture (1/1); 60 mg (2 eq) of 3- [bis (2-carboxyethyl) -phosphino] propanoic acid hydrochloride hydrate in solution in 1 mL water and 21 mg (4 eq) sodium bicarbonate solution in 1 mL of water are added to the mixture. After stirring for 30 minutes at 40 ° C. under an inert atmosphere, the analyzes indicate that the mixture contains most of the expected product [1].

  LC-MS analysis: LC-DAD (400-700 nm) Column: Waters XTerra MS C18 5pm (4.6 x 50) mm Mobile phase: A: Water + formic acid 0.1% / B: acetonitrile Linear gradient: T (min) A % / B%: 0 min 95/5; 8 min 0/100 Flow rate: 1 mL / min. Detection: UV diode array at = 400-700nm

  Retention time t = 4.9 min. Relative purity> 95% MS (ESI +) m / z = 311 corresponds to the mass peak of the expected product monocation [1] EXAMPLE OF COLORING Staining process 10 ml of fresh solution of the compound [1] of the synthetic example are applied on a lock of 1 g hair of pitch 4 arranged at the bottom of the same bowl for 30 minutes at room temperature (the locks are returned and re-treated after 15 minutes). The locks are then rinsed with running water and dried.

  After staining, the pitch lock 4 became visually brighter than untreated control locks.

  Remanence vis-à-vis successive shampoos:

  The locks thus treated are divided in two, one half is subjected to 5 successive shampoos in a cycle which comprises wetting the locks with water, washing with a conventional shampoo, rinsing with water followed by drying.

  Visual Observations During shampoos, there is no visible bleeding, shampoo foam and rinsing water are not colored. The lightening effect remains visible on the hair of 4 pitch thus treated. Results in the L * a * b * system

  The color of the locks before and after the 5 washings was evaluated in the L * a * b * system by means of a KONICA MINOLTA CM 2600 spectrophotometer (Illuminant D65). In this system L * a * b *, L * represents the intensity of the color, a * indicates the green / red color axis and b * the blue / yellow color axis. The higher the L value, the lighter or less intense the color. Conversely, the lower the value of L, the darker or more intense the color. The higher the value of a * the hue is red and the higher the value of b * the hue is yellow. The variation of the coloration between the strands of HT 4 hair and the strands of hair after treatment (staining, or staining and successive washings) is measured by (AE) according to the following equation: ## EQU1 ## In this equation, L *, a * and b * represent the measured values before staining and Lo *, ao * and bo * represent the values measured after treatment (staining, or staining and The higher the value of AE, the greater the difference in color between the locks HT 4 and the colored locks 15 AE AE of the lock HT 4 after application of the compound (1) 3.02 according to the invention AE Wicks HT4 after application of the compound (1) 4.63 according to the invention and then 5 successive shampoos The results of the table shows that there is no significant difference in color variation even after 5 shampoos. the lightening effect on the hair remains almost unchanged c e which shows a very good resistance to shampoos dyes of the invention. Reflectance Results The lightening performance of the compositions according to the invention and their persistence with regard to successive shampoos were expressed as a function of the reflectance of the hair. These reflectances are compared to the reflectance of an untreated strand of HT4 pitch hair.

  The reflectance is measured using a KONIKAMINOLTA spectrophotocolorimeter, CM 2600d and after irradiation of the hair with visible light in the wavelength range of 400 to 700 nanometers.

  It is firstly noted that the reflectance of a lock of hair treated with a composition according to the invention is greater than that of untreated hair. The treated locks therefore appear clearer. In addition, the results show that the reflectance of the locks of hair of pitch 4 treated with the composition of the invention evolve very little even after 5 shampoos. Thus the coloration and the lightening effect on the hair remain virtually unchanged which shows a very good resistance to shampoos dyes of the invention. Reflectance of Wicks Treated with Compound 1 at Application and After 5 Shampoos Wavelength (nm) Reference Compound 1

  Compound 1 - 5 shampoos 6-5-4-3-2-1-0

Claims (22)

  1. Fluorescent dye of formula (I) below: Rh + iTa / SY - (CRIR2) m N (CR3R4) n (I) its organic or inorganic acid salts, optical isomers, geometric isomers, and solvates such as hydrates; formula (I) in which: hep represents a saturated or unsaturated heterocyclic group; • Rg, R'g, Rh and R'h, identical or different, represent a hydrogen atom, halogen, an amino group, (di) (C 1 -C 4) alkylamino, cyano, carboxy, hydroxy, trifluoromethyl , C 1 -C 4 alkoxycarbonyl, (C 1 -C 4) alkoxycarbonyl, (C 1 -C 4) alkylcarbonyloxy, C 1 -C 4 alkoxycarbonyl, C 1 -C 4 alkoxycarbonylamino, acylamino, carbamoyl, (C 1 -C 4) alkylsulfonylamino an aminosulfonyl radical, or a (C 1 -C 16) alkyl radical optionally substituted with a group chosen from (C 1 -C 12) alkoxy, hydroxy, cyano, carboxy, amino, (di) (C 1 -C 4) alkylamino, or then the two alkyl radicals carried by the nitrogen atom of the amino group form a heterocycle comprising from 5 to 7 members and optionally comprising another heteroatom identical to or different from that of the nitrogen atom; - R; and R ', which may be identical or different, represent a hydrogen atom or a (C 1 -C 4) alkyl group; R 3, R 2, R 3 and R 4, which may be identical or different, represent a hydrogen atom or a (C 1 -C 4) alkyl, (C 1 -C 4) alkoxy, hydroxy, cyano, carboxy or amino (C 1 -C 4) group; ) alkylamino, (C1-C4) dialkylamino, said alkyl radicals being able to form, with the nitrogen atom which carries them, a 5- to 7-membered heterocycle, optionally comprising another heteroatom different or different from nitrogen; Ta is: i) a covalent bond a; ii) one or more radicals or combinations thereof selected from -SO2-, -O0, -S0, -N (R) u, uN + (R) (R) u, uC (O) u, with R and R, same or different , representing a hydrogen atom, a C1-C4 alkyl, C1-C4 hydroxyalkyl or a (C1-C4) alkyl radical; iii) a heterocycloalkyl or heteroaryl radical, cationic or non-cationic; m and n, identical or different, represent an integer inclusive between 0 and 6 with m + n represents an integer inclusive between 1 and 10; M 'representing an anionic counterion; and Y represents: i) a hydrogen atom; ii) an alkali metal; iii) an alkaline earth metal; iv) an ammonium group: N + RaRRRYR8 or a phosphonium group: P + RaRRRYR8 with Ra, RR, R7 and R8, which may be identical or different, representing a hydrogen atom or a (C 1 -C 4) alkyl group; or v) a thiol protecting group; it being understood that: - when the compound of formula (I) contains other cationic parts, it is associated with one or more anionic counter-ions making it possible to reach the electroneutrality of formula (I).   2. Fluorescent dye of formula (I) according to the preceding claim wherein Y represents a hydrogen atom, or an alkali metal.   3. Fluorescent dye of formula (I) according to claim 1 wherein Y represents a protecting group.   4. Fluorescent dye of formula (I) according to the preceding claim wherein Y represents a protective group selected from the following radicals: - (C1-C4) alkylcarbonyl; - (C1-C4) alkylthiocarbonyl; - (C1-C4) alkoxycarbonyl; - (C1-C4) alkoxythiocarbonyl; - (C1-C4) alkylthiothiocarbonyl; - (di) (C1-C4) (alkyl) aminocarbonyl; - (di) (C1-C4) (alkyl) aminothiocarbonyl; arylcarbonyl, 20-aryloxycarbonyl; aryl (C1-C4) alkoxycarbonyl; - (di) (C1-C4) (alkyl) aminocarbonyl; - (C1-C4) (alkyl) arylaminocarbonyl; carboxy; - S03; M + with M + representing an alkali metal or M 'of the formula (I) and M + are absent; optionally substituted aryl, optionally substituted heteroaryl; optionally substituted heterocycloalkyl, optionally cationic; isothiouronium -C (NR 'R'd) = N + R'eR'f; With R ', R'd, R'e and R'f, identical or different, represent a hydrogen atom or an alkyl group; preferentially R 'to R' f represent a hydrogen atom; and An-represents an anionic counterion; - isothiourea -C (NR 'R'd) = NR'e; with R ', R'd and R'e are as defined previously; - (di) arylalkyl optionally substituted; optionally substituted (di) heteroarylalkyl; - CR'1R'2R'3 with R'1, R'2 and R'3 identical or different, representing a halogen atom or a group selected from: alkyl; alkoxy; optionally substituted aryl; optionally substituted heteroaryl; - P (Z ') R "1R" 2R "3 with R" 1, and R "2 identical or different represent a hydroxy, alkoxy or alkyl group, R" 3 represents a hydroxyl or alkoxy group, and Z' represents an atom oxygen or sulfur; -cyclic sterically hindered; and - optionally substituted (C.sub.1 -C.sub.4) alkyloxy.   5. Fluorescent dye of formula (I) according to any one of the preceding claims wherein Y represents an alkali metal or a protective group chosen from: - (C 1 -C 4) alkylcarbonyl; -arylcarbonyl; - (C1-C4) alkoxycarbonyl; aryloxycarbonyl; aryl (C1-C4) alkoxycarbonyl; - (di) (C1-C4) (alkyl) aminocarbonyl; - (C1-C4) (alkyl) arylaminocarbonyl; optionally substituted aryl; 5- or 6-membered cationic monocyclic heteroaryl; 8 to 11-membered cationic bicyclic heteroaryl; cationic heterocycle of the following formula: Me N ~ N -Anothothuronium -C (NH2) = N + H2; An; -isothiourea -C (NH2) = NH; and - S03; W.   6. Fluorescent dye according to any one of the preceding claims belonging to the formula (la) which has the ethylene group connecting the pyridinium portion to the phenyl in the ortho or para position is in positions 4-4 ', 4-2', or 2 -4 ': with for formulas (la): Hét Nù represents a saturated or unsaturated heterocyclic group; monocyclic compound comprising 5 to 7 members and having 1 or two heteroatoms selected from nitrogen, oxygen or sulfur, particularly the heteroatom is a nitrogen atom; - Rg, R'g, Rh and R'h, identical or different, represent a hydrogen atom or a group (C1-C4) alkyl; Ta represents a covalent bond a, or a group selected from: ## EQU1 ## where R (R) u (C) O (C) O (C) O (C) and wherein R, R + (R) (R), where R, R being the same or different, representing a hydrogen atom, a C1-C4 alkyl group; m and n, which are identical or different, represent an integer inclusive between 0 and 6 with m + n represents an integer between 2 and 6 inclusive; M 'representing an anionic counterion; and Y is as defined above; it being understood that: the function SY may be in the covalent -SY or ionic form -S Y + depending on the nature of Y and the pH of the medium, and when the compound of formula (Ia) contains other cationic parts, is associated with one or more anionic counterions to achieve the electroneutrality of the formula (la).   7. Heterocyclic thiol fluorescent dye according to any one of the preceding claims, selected from the following dyes: / SH NIN / - SM 'CN / - M' 1 2 H_NN / / N 'SH IN / \ N' M ' M / N / CN / CN / CNS / CNS / CNS / CNS / CNS / CNS / CNS -NM '\ N + M' ~ / -NJNOH 9 10 ON \ N_ CN \ / \ V) = - N 'N ~ NJ ~ r 2M' M '11 12 CN / \ 2M' / / \ NOS \ 13 With M representing an anionic counterion.   8. Dyeing composition comprising in a suitable cosmetic medium, a thiol fluorescent dye of formula (I) as defined in any one of claims 1 to 7.   9. Dyeing composition comprising in a suitable cosmetic medium, at least one thiol fluorescent dye of formula (I) as defined in any one of claims 1 to 7 and at least one reducing agent.   10. Dyeing composition according to the preceding claim wherein the reducing agent is chosen from: cysteine, homocysteine, thiolactic acid, the salts of these thiols, phosphines, bisulfite, sulfites, thioglycolic acid, as well as its esters, borohydrides and their derivatives, the sodium, lithium, potassium, calcium and quaternary ammonium salts; catecholborane.   11. Composition according to any one of claims 8 to 10, wherein the heterocyclic thiol fluorescent dye of formula (I) is present in an amount of between 0.001 and 50% by weight relative to the total weight of the composition. 20   12. A process for dyeing keratin materials, wherein a dye composition as defined in any one of Claims 8 to 11, comprising, in a suitable cosmetic medium, at least one thiol fluorescent dye of formula (I), is applied to the materials. as defined in any one of claims 1 to 7, optionally in the presence of a reducing agent capable of reducing the disulfide bonds of the keratin materials.   13. The method of dyeing according to the preceding claim wherein when the thiol fluorescent dye of formula (I) comprises a protecting Y group, the application is preceded by a deprotection step.   14. A method of dyeing keratin materials according to any one of claims 12 or 13 characterized in that the keratin materials are dark keratinous fibers having a pitch of less than or equal to 6.   15. A process according to any one of claims 12 to 14 wherein the reducing agent is applied before or after the application of thiol fluorescent dye.   The process of any one of claims 12 to 15, wherein the composition comprises an oxidizing agent.   17. A method according to any one of claims 12 to 16 comprising an additional step of applying to the keratin fibers an oxidizing agent.   18. A multi-compartment device in which a first compartment contains a dye composition comprising a thiol fluorescent dye as defined in claims 1 to 7 and a second compartment contains a reducing agent capable of reducing the disulfide bonds of the keratin materials.   19. Device according to the preceding claim comprising a third compartment which contains an oxidizing agent.   20. Use of fluorescent dyes thiols as defined in claims 1 to 7 for dyeing dark human keratin fibers.   21. Use according to the preceding claim for lightening dark keratin fibers. 25   22. Use according to claims 20 or 21 characterized in that the keratinous fibers have a pitch of less than 6. 15